Some modification is needed to fit the RB67 Pro SD backs as the insert section of the back is slightly bigger. I have modified the Camo ZONE body but don't want to share the file on Thingiverse. Below is an image of the new dimensions. In Fusion 360 all you need to do is create a rectangle 83.80mm wide, place it 6.75mm above the mount face, then extrude up and across and much as you need to make the cutout using Combine > Cut. It will expose the slots for the viewfinder nuts a bit but it shouldn't be a major problem.
This modification should still allow mounting of the older backs.